During the process of drilling oil and gas wells, drill bit cuttings are produced by the drill bit as it bores the well bore. The well bore fluid or mud carries the cuttings to the well surface. Some of the cuttings are separated at the surface, but some remain in the mud, which is re-circulated down the work string in the well bore. The mud being re-circulated down hole may also pick up scale from the work string. Debris entrained within the mud is problematic. The debris can cause bottom-hole assemblies such as drill bits, drill motors, measurement while drilling tools, and other components to malfunction. Down hole mud screens have been developed to filter the mud before the fluid is introduced to the bottom-hole assemblies.
Applicant's U.S. Pat. No. 7,549,486 (which is incorporated herein by reference) is titled “Screen Apparatus and Method.” The patent discloses a mud screen having either a uniform outer diameter or a mud screen having two discrete sections, each section having a different outer diameter. The patent discloses a series of longitudinal openings for passage of the filtered fluid through the mud screen to the drill pipe.
Although down hole mud screens reduce the frequency at which bottom-hole assemblies malfunction, bottom-hole assemblies must still be removed from time to time. For example, the bottom-hole assembly may require repair or maintenance. Also, the need for certain bottom-hole assemblies may end before the drilling of the well bore is complete. To facilitate the removal of bottom-hole assemblies positioned below mud screens, conventional down hole mud screens must be removed from the well bore. This additional step of removing the entire down hole mud screen is time consuming and expensive, especially when the removal of the mud screen is not necessary for any other purpose. There is a need for a device that can be used to effectively filter debris from a well bore and that can facilitate the removal of a bottom-hole assembly positioned below the device while the device remains in the well bore.